Current methods of determining high intensity focused ultrasound (HIFU) fields in tissue rely on extrapolation of measurements in water assuming linear wave propagation both in water and in tissue. Neglecting nonlinear propagation effects in the derating process can result in significant errors. A new method based on scaling the source amplitude is introduced to estimate focal parameters of nonlinear HIFU fields in tissue. Focal values of acoustic field parameters in absorptive tissue are obtained from a numerical solution to a KZK-type equation and are compared to those simulated for propagation in water. Focal wave-forms, peak pressures, and intensities are calculated over a wide range of source outputs and linear focusing gains. Our modeling indicates, that for the high gain sources which are typically used in therapeutic medical applications, the focal field parameters derated with our method agree well with numerical simulation in tissue. The feasibility of the derating method is demonstrated experimentally in excised bovine liver tissue.

中文翻译：

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一种用于高强度聚焦超声治疗应用的降额方法。

确定组织中高强度聚焦超声 (HIFU) 场的当前方法依赖于假设在水中和组织中线性波传播的水中测量值的外推。在降额过程中忽略非线性传播效应会导致重大误差。引入了一种基于缩放源幅度的新方法来估计组织中非线性 HIFU 场的焦距参数。吸收组织中声场参数的焦点值是从 KZK 型方程的数值解中获得的，并将其与模拟在水中传播的那些值进行比较。焦点波形、峰值压力和强度是在宽范围的源输出和线性聚焦增益下计算的。我们的模型表明，对于通常用于治疗医学应用的高增益源，用我们的方法降低的焦场参数与组织中的数值模拟非常吻合。在切除的牛肝组织中通过实验证明了降额方法的可行性。